The K-Zone: Honda ATC100 off-road trike

Age: about 25 years
Cost: about Ł150 (bought in auction with other stuff, so not sure)
Insurance: n/a
Economy: unknown
Good points: goes anywhere off-road, lasts forever
Bad points: no good on tarmac (not road legal anyway)

Machines like this one started the all-terrain vehicle craze 30-odd years ago. After 25 years and countless muddy miles, this one is still going strong
Although 3-wheeled and 4-wheeled motorcycles had been produced in limited numbers for agriculture and rural transportation prior to the 1970s, the modern `all-terrain vehicle' (ATV) really has its roots in leisure, not work. The first mass-produced, recognizably modern ATV was Honda's US90, released in the USA in 1970. This three-wheeled, 90cc machine was a huge success -- mostly among urban, rather than rural, off-road riders. The ATC110 (ATC stands for `all-terrain cycle'), released in the USA in 1979, was only an incremental development of the US90. Although it has a larger engine, the ATC110 has the same air-cooled, four-stroke engine arrangement, the same four-speed, dual range gearbox, the same chassis, almost the same balloon tyres, and the same styling. In both machines, the emphasis is on robust simplicity. There is no electronic ignition, no cooling system, no indicators or clocks, no electric start, a single brake, no differential gear, and no suspension.
Honda went on to produce larger ATC models -- and models with electric start, suspension, etc -- but these days the company's off-road offerings are all four-wheelers. Other companies have produced three-wheeled ATVs, but they don't seem to have achieved the same popularity as the Hondas. In the meantime, four-wheeled ATVs have taken over almost completely from the popular 3-wheelers of the 80s, and there is a glut of cheap, nasty machines on the market at the moment.

History and condition

My particular machine is a 1981 model. It's been somewhat modified, either for racing or to look like it's been racing -- it isn't easy to tell which. The front and rear lamps are gone along with their switches; if the machine ever had a front brake (not all the early ones did), it's gone; probably the only reason it still has the rear grab bar is that it's difficult to get the machine onto a trailer without it; the handlebars probably aren't original; and the lever throttle has been replaced by a more usual twist-grip. There's some superficial rust, but there doesn't appear to be any deep corrosion in the structural metalwork. Part of the left mudguard has snapped off, and the rest of the plastic bodywork is rather tatty. In particular, the plastic has been crudely cut around the petrol tank, which I assume is slightly larger that the original. The seat has been covered with black packing tape, which is not unusual for a machine of this age -- the seat covers were prone to rot away. All the gears engage, although they're a bit clonky. There are no obvious oil leaks. The hi-low gear selector is extremely stiff, but works. The pull-start unit is not very reliable, but the machine starts with a push a couple of yards in second gear. Once started, it needs a bit of throttle for a few seconds before it will idle -- there is a choke (on the carburettor body), but it doesn't make an enormous difference.
In short, it's a runner, and a reasonably good runner at that. When I bought it I had to rewire the engine stop switch, because a previous owner had connected it to the disconnected headlamp wiring, for some reason. I also had to replace the spark plug (not a common model, but not difficult to get from a specialist supplier). But apart from that, I didn't have to do much else to get it going. I'm not sure how much I paid for this trike, because I bought it with some other stuff. But it seems to be possible to get one in this condition for £150- £300 on eBay. I don't think you'd get any other adult-sized off-road vehicle for this sort of money, whatever the age.

Engine, gearbox, etc

The trike in its element -- 3 up, bouncing along a rutted farm track. Lack of suspension makes for an interesting ride

he ATC100 has a four-stroke, air-cooled engine. It's a very simple design, and anybody with a reasonable grasp of automotive engineering will recognize all the parts in it. The ignition system consists of a coil, a condenser (capacitor), and a contact breaker -- just like the Austin A30 your granddad had. The engine ticks over quietly, but there's not much of a muffler on the exhaust, so it makes a loud-ish rasp with the throttle open. The clutch is automatic, and operated by engine speed. At tick-over, the trike will stand still in any gear, and with the low gear range selected, it will pull from idle in first, second, or third gear. To change gear, it is necessary to close the throttle completely. Even then, gear changes are a bit clonky.

Running gear

The ATC has a simple chain drive, much like a motorcycle. The chain is fully enclosed, which keeps the mud and grot off it, and stops bramble and undergrowth getting caught in it. The downside is that it's difficult to check the chain wear and tension without removing the cover. There is a single rear brake -- there may have been a front brake at some point, but it's not certain. Early ATCs had only a rear brake, and both the hand brake lever and foot brake operated it. The tyres are enormous balloons, designed to run at about 2-3 psi.

Riding it

Riding an off-road trike is not like riding or driving anything else. Like most four-wheeled ATVs, the ATC has no rear differential gear. That is, the rear wheels are on a fixed axle and must rotate at the same speed. Because cornering requires that one wheel travel further than the other, road-going vehicles, and some of the more expensive ATVs, have a differential gear. This allows the driving wheels to turn at different speeds, even though both are being driven by the engine. Unlike a four-wheeled ATV, the ATC has the added complication of having only three wheels.
      In any event, steering and cornering on the ATC requires a particular technique. You can't just turn the handlebars -- if you do, you'll find that you keep going in a straight line with the front wheel at an angle to the direction of motion. This is certainly a disconcerting experience the first time it happens. The trick, which takes some mastering, is to sit as far forward as you can -- almost on the petrol tank -- and put your weight on one footpeg as you corner. Shifting your weight forward increases traction on the front tyre. The side to which you have to shift your bodyweight differs according to speed. At low speeds, you need to shift your weight away from the turn, to allow the wheel on the inside of the turn to slip. At high speeds, you need to shift into the turn, to counteract the tendency of centrifugal force to lift the inside wheel. It's also necessary to oversteer, particularly at low speeds. The heavy pulling on the bars, coupled with the need to throw your weight around, makes riding the ATC rather more like skiing than motorcycling -- it requires concentration and a great deal of effort. In common with skiing, it's actually harder to pootle around slowly than it is to grit your teeth and go for it.
      In short, riding the ATC requires techniques that are almost the opposite to those which work on a two-wheeled motorcycle; ride the ATC like a bike, and you'll soon be in a ditch. I'd certainly recommend practising in the middle of a big field until you get the hang of it. It's also worth noting that, although the ATC rides well enough on gravel (allowing for the unconventional cornering technique) it performs very badly indeed on paved roads. To be fair, the user's manual is very clear that the machine is not designed for road use.
      The lack of suspension doesn't seem to be a huge problem, mostly because of the elasticity of the air in the huge balloon tyres. I've been riding it on ground littered with tree stumps (2-4 inches high), and it copes well enough.The ATC will negotiate a sudden step of about six inches without complaining, but it could jar the fillings out of your teeth if you do it too often.
      Once you get the hang of the riding technique, the ATC will negotiate some fairly tricky terrain -- certainly tricky enough to defeat most other off-road vehicles. Because it's only 3 feet wide, the ATC is capable of crossing dense, rutted woodland, as well as open spaces. And because it weighs `only' 200 lbs, if it does get stuck somewhere I can generally heave it out by brute force.

Conclusion

A three-wheeled off-road vehicle has certain advantages over a four-wheeled one. Most obviously, a three-wheeler is significantly lighter, all other things being equal. In my (albeit limited) experience, the ATC manoevres better at low speeds than a fixed-axle four-wheeler. However, it is harder to keep stable, particular at speed. The fact that a four-wheeler is easier to handle may explain why nobody makes anything like the ATC any more.
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